Takes out wide breakpoint on sticky bar in Discussions
Takes out wide breakpoint on sticky bar in Discussions

refs: CNVS-27362

Test Plan:
- Go to discussions, make sure you have one with a lot of comments so
the page will scroll
- As you scroll down you'll notice the sticky top bar. The bar no longer
changes margins along the side when browser width is resized
Note: if you're looking at this pre-navigation fix, you'll notice the
global navigation moving. That's expected.

Screenshot - http://cl.ly/0f0p2K1z0b3x

Change-Id: I28f97d0aa88ba2d788020360b098035ee08e3d5e
Reviewed-on: https://gerrit.instructure.com/73994
Tested-by: Jenkins
Reviewed-by: Pam Hiett <7b533437add1ce4ea4ed79979fa88e0e484e554b@instructure.com>
Product-Review: Pam Hiett <7b533437add1ce4ea4ed79979fa88e0e484e554b@instructure.com>
QA-Review: Nathan Rogowski <2e8aa918660411855c6d44d5bb2da677aa033255@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,HotChalk/canvas-lms,roxolan/canvas-lms,matematikk-mooc/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,SwinburneOnline/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,dgynn/canvas-lms,djbender/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,grahamb/canvas-lms,djbender/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,grahamb/canvas-lms,fronteerio/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,fronteerio/canvas-lms,SwinburneOnline/canvas-lms,roxolan/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,dgynn/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,matematikk-mooc/canvas-lms,dgynn/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,dgynn/canvas-lms,fronteerio/canvas-lms